1. Field of the Invention
This invention relates to a batch fabricated multiple element keyboard switch assembly and more particularly to such an assembly providing electrical contact closure at a plurality of separate conductive engagement regions.
2. Discussion of the Prior Art
In order to be competitive in a high volume market such as the calculator market of the Touch-Tone telephone market a keyboard switch assembly must satisfy a large number of conflicting demands. It must be compact, lightweight, very inexpensive, and highly reliable and have a satisfying touch to the operator. While electronic debouncing circuits are available, the economics of a particular use or the requirements of a particular customer frequently necessitate the use of a bounce-free switch assembly. That is, a single, unambiguous contact closure signal is required for each activation of a keyboard key. This problem of providing bounce-free operation becomes worse in multi-pole switch assemblies such as arrangements wherein a single key actuation must connect separate row and column conductors to a common voltage.
A variety of keyboard switch assembly arrangements have been developed in an attempt to meet the demands of the keyboard market. These include arrangements described in the following U.S. Pat. Nos. 3,699,294 to Suddath, 3,707,609 to Dupont et al, 3,780,237 to Seeger, Jr. et al, and 3,860,771 to Lynn et al.
Such arrangements teach the use of batch fabricated keyboard switch assemblies with switch contacts printed on substrates and with flexible protrusions or bubbles, sometimes used in combination with springs to improve switch characteristics. Nonetheless, further improvements in switch characteristics, and particularly elimination of switch bounce remain as goals to be sought.